This data comes from the 2016 New Coder Survey conducted by Free Code Camp, and created by Quincy Larson and Saron Yitbarek. The survey had 15,620 responses to 43 questions; some questions were asked only as a follow-up, and none were required. Of the 43 questions, 22 were demographic questions and the rest related to coding.
You can find a more detailed breakdown of the dataset here.
Created by Evan Balzuweit and Kelly Stathis.